1. Field of the Invention
The invention relates to atomic layer deposition.
2. Description of the Related Art
Atomic layer deposition (ALD), for example, disclosed in U.S. Pat. No. 6,764,927, is a well known deposition technique in the semiconductor industry. ALD employs a precursor and a reactive gas to from an ALD layer on a substrate in a chamber.
The deposited ALD layer typically suffers from issues such as pinholes, or low density, leading to leakage current when applied in PMOS or NMOS transistors. U.S. Pat. No. 6,723,581 discloses forming a substantially-hydroxylated SiOxHy layer (e.g. 3×1014 hydroxyl per cm2) by immersing a silicon substrate in a solution comprising de-ionized water and ozone to facilitate growth of the ALD layer. Then, an ALD layer is deposited on the substantially-hydroxylated surface by repeated cycles of ALD layer growth. Each cycle of the ALD layer growth consists of about 400 ms pulse of H2O, about 200 ms pulse of HfCl4 and several seconds pulse of N2. However, the ALD layer thus formed still suffers from insufficient density.
Accordingly, a denser ALD layer capable of solving the described issues is desirable.